Lubricant compositions



United States Patent 3,255,114 LUBRICANT COMPOSITIONS Louis de Vries, Richmond, Calif., assignor to Chevron Research Company, a corporation of Delaware No Drawing. Filed Sept. 9, 1963, Ser. No. 307,308 6 Claims. (Cl. 25256) This invention relates to novel lubricant compositions and it is particularly directed to lubricant compositions containing copolymersformed from polyglycol azo ester compositions and alkyl esters of a,B-unsaturated monocarboxylic acids which are adapted to be employed in internal combustion engines.

The primary function of a lubricating composition is to lubricate. Involved in this process is the reduction of friction and decrease of engine part wear. In performing this function the lubricant is subjected to deterioration, principally by oxidation, and contamination by the resulting oxidation products. These contaminants may deposit out on portions of the engine communicating with the lubricant and thereby inhibit efficient engine operation, increase cylinder wall wear and increase oil losses from line plugging. Additives which enhance the detergent characteristics of the lubricant are employed to overcome or minimize these deleterious interference with engine lubrication. These additives function essentially as dispersants to prevent oil oxidation products as Well as fuel soot, resin, and other oil-insoluble materials from settling and depositing on engine parts.

Both metal-containing and metal-free compositions have been used as detergent additives. The former, however, may themselves. be a source of harmful engine deposits since whenever oil is subjected to. oxidation conditions any metal-containing additives present in the oil may form an ash which is partially deposited out on engine surfaces. Because of this possibility, various metal-free detergent additives, commonly called ashless detergents, were developed. When oxidized these detergents leave no harmful ash to deposit out on engine parts. Illustrative examples of this type detergent additive. appear in US. Patent No. 2,892,783.

The new lubricating compositions of the present invention contain remarkable new additives of the ashless detergent variety. These new ashless detergent additives are block copolymers formed from polyglycol azo ester compositions and alkyl esters of the a, 8-unsaturated monocarboxylic acids such as acrylic, methacrylic, crotonic, tiglic, a-ethylacrylic, a-methylcrotonic, a-ethylcrotonic, fl-et-hylcrotonic, fi-propylcrotonic, and the like. In the block structure of the new copolymers the polyglycol constituent appears in blocks which are linked to blocks of the anti-unsaturated monocarboxylic acid ester complement. In contrast, previous copolymer ashless detergent additives formed from such acids and polyglycols have random structures. In such a structure the constituents do not orient themselves in a definite pattern; hence, they are referred to as random copolymers. Peptization tests indicate the new lubricant compositions containing the novel block copolymers have superior dispersant qualities to lubricants containing the conventional random copolymers.

The block copolymers of the instant invention may be prepared by reacting a polyglycol azoester of the general formula: I i

ON=NC 6 3. Pt. Pt.

part of the new copolymers.

Fatented June 7, 1966 wherein R R R and R represent alkyl radicals and P.G. represents a polyglycol group, with an alkyl methacrylate of the formula:

1? O Hz=C-C 'OR5 wherein R is a hydrocarbon group containing from 4 to 30 aliphatic carbon atoms, to obtain a copolymer lubricant ashless detergent additive of the general formula:

wherein the above formulae R R R and R represent alkyl radicals having from 1 to about 7 carbon atoms and preferably represents a methyl radical. P.G. suitably represents a polyalkylene glycol group derived from a poly-1,2-alkylene glycol or its monoalkyl ether, said ether having from 1 to 18 carbon atoms in the alkyl group, bot-h ether and glycol having from about 2 to about 500 alkylene oxide units. It is preferable that P.G. represents a polyethylene oxide or polypropylene oxide group having from about 40 to about 500 alkylene oxide units. R preferably represents alkyl radicals having from about 8 to about 18 carbon atoms, and n represents the number of times the bracketed portion occurs and ranges from about 20 to about 5000.

In the above reaction the polyglycol azo ester serves a dual function. It serves as an initiator in the copolymerization by means of a free radical mechanism. In addition, it supplies the polyglycol groups which form The polygylcol groups impart polarity to the composition whereas the methacrylate portion imparts oil solubility. These factors add to the dispersant and wear resistant properties of the additive, respectively.

The novel lubricant compositions of the, present invention comprise a major portion of an oil of lubricating viscosity and a minor portion suificient to enhance the detergent characteristics of the composition of the abovedescribed, copolymer composition.

The following example is illustrative of the invention.

EXAMPLE Preparation of polyglycol azo 'esler initiator Into a flask was charged 224 g. of polyethylene glycol having a molecular weight of approximately 200 dissolved in 750 cc. of benzene. to remove as much Water as possible by such means. and then. dried further over calcium hydride overnight. The benzene solution Was then filtered off the calcium hydride and added to 270 cc. of dry dioxane (dried by refluxing over sodium for 48 hours, followed by distillation), which contained 8.7 g. of azodiisobutyronitrile. The combined solutions were saturated with dry HCl gas at 0 C. and allowed to stand in a cold room at 0 C. for' 5 days. The imido ester hydrochloride product was then precipitated by addition ofpentane. The excess azodiisobutyronitrile remained in solution. redissolved in benzene and reprecipitated' with pentane. The product was now dissolvedin a small amount of dioxane and hydrolyzed by the addition of 10 cc. of water. The removal of the dioxane and water'byfreeze This mixture was refluxed.

The precipitate was" drying yielded the polygylcol azo ester product. The product was further purified as follows: The product was dissolved in acetone and the excess hydrochloric acid was precipitated with ammonia gas. The acetone solution was filtered off the ammonium chloride and the solvent was removed in a vacuum. The solid residue was dissolved -in benzene and the pure initiator was obtained from this solution by freeze-drying.

Preparation of block copolymer In a 2000 ml. 3-neck round bottom flask were placed 670 cc. of benzene, 250 cc. of dodecyl methacrylate (distilled) and 80 cc. of a solution of 125 g. of the polyglycol azo ester initiator in 500 cc. of benzene. The contents Were heated to reflux. The rest of the initiator solution was now added at a rate of 5.8 cc./ minutes and simultaneously dodecyl methacrylate was added at a rate of 5.8 cc./ 10 minutes. The additions were continued for 2 /2 hours after which time 95 cc. of dodecyl methacrylate and 360 cc. of initiator solution had been added. The copolymer was now precipitated by the addition of excess methanol and was redissolved and reprecipitated two times. After drying, the yield was 213 g. From viscosity measurements the mol weight of the copolymer appeared to be approximately 80,000.

In an entirely analogous fashion a block copolymer was prepared using a polygylcol azo ester initiator formed with a polyethylene glycol having a molecular weight of approximately 12,000. Dodecyl methacrylate was again employed.

Peptization tests were used to evaluate the performance of the novel block copolymer ashless detergent additives. Particularly, the graphite and asphaltene tests were employed. The former test in general consists of mixing 0.5 gram of graphite with 100 cc. of lubricating oil containing 0.1 gram of copolymer and measuring the time required for the graphite to settle from the mixture. Comparison of the settling times of various lubrieating oil compositions produces a relative evaluation of their dispersant characteristics. Effective dispersant compositions exhibit less than 10% sedimentation after 12 hours standing whereas unsatisfactory compositions give as high as 95% sedimentation. In the asphaltene test 5 cc. of a 5% solution of the dry polyglycol polymeric additive is mixed with 2 cc. of a 1% solution of airblown Midway Asphalt in benzene. The mixture is diluted to cc. with n-pentane. This diluted mixture is shaken up and observed for two minutes. If no coagulation occurs, 2 cc. of glacial acetic acid is added and the time to the first coagulation of asphalt is recorded. Coagulation times of minutes or more indicate effective dispersants. In such tests the dispersant qualities of oils containing the novel copolymers of this invention are found to be superior to those containing pure polydodecyl methacrylate and those containing random copolymers formed from mixed alkyl methacrylates and polyethylene glycol, recognized heretofore as unusually effective dispersants.

As mentioned above, the lubricant compositions of this invention contain a minor portion of the additive sufficient to enhance the detergent characteristics of the composition. Usually amounts of 0.1% to 10% by weight, preferably 0.25% to 5% by weight, are; employed. Concentrates containing up to 60% to 75% or higher are also within the scope of the invention.

Lubricating oils which can be used as base oils inelude a wide variety, such as naphthenic base, paraflin base, and mixed base mineral lubricating oils; and synthetic oils, such as polymers of propylene, butylene, etc., propylene oxide polymers, dicarboxylic acid esters, such as those which are prepared by esterifying azelaic acid with 2-ethylhexyl alcohol and silicon esters, such as tetraethyl silicate, hexa(4-methyl-2-pentoxy)-disiloxane, etc.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary 1im with an alkyl methacrylate of the formula:

II CH2=CI-C-OR5 to obtain a copolymer lubricant ashless detergent additive having the structural formula:

R1 CH: Er c Clix-( 1 H 1=O O=( 3 Pi l. 1 4.5 11

wherein the above formulae R R R and R represent alkyl radicals having from 1 to about 7 carbon atoms, R6. represents a polyalkylene glycol group having from about 40 to about 500 alkylene oxide units and from 2 to 3 carbon atoms in each of said units, R represents an alkyl radical having from about 8 to about 18 carbon atoms and n represents an integer from about 20 to about 5000.

2. The method of claim 1, wherein R R R and R are methyl radicals, P.G. is a polyethylene glycol group having from about 40 to about 500 ethylene oxide units and the alkyl methacrylate is dodecyl methacrylate.

3. A copolymer lubricant ashless detergent additive composition having the general formula:

wherein R and R represent alkyl radicals having from 1 to about 7 carbon atoms, R represents an alkyl radical having from about 8 to about 18 carbon atoms, P.G. represents a polyalkylene glycol group having from about 40 to about 500 alkylene oxide units and from 2 to 3 carbon atoms in each of said units, and n represents an integer from about 20 to about 5000.

4. The composition of claim 3, wherein R and R are methyl radicals and R6. is a polyethylene glycol group having from about 40 to about 500 ethylene oxide units.

5. A lubricant composition comprising a major pro portion of an oil of lubricating viscosity and a minor proportion sufiicient to enhance the detergent characteristics of the composition of a copolymer having the structural formula:

R1 (III-Ia "I R2C o H2-0 -n l I P.G.

5 a 6 wherein R and R represent alkyl radicals having from References Cited by the Examiner 1 to about 7 carbon atoms, R represents an alkyl radical UNITED STATES PATENTS having from about 8 to 18 carbon atoms, R6. represents 7 a polyalkylene glycol group having from about 40 to 2,586,995 2/1952 Robertson 260-895 about 500 alkylene oxide units and from 2 to 3 carbon 5 2,744,105 5/1956 Barney 260 89-5 atoms in each of said units, and n represents an integer 3,189,586 5/1965 Smart et 260'89-5 from about 20 to about 5000.

6. The composition of claim 5, wherein R and R are DANIEL WYMAN Pnmary Examiner methyl radicals and R6. is a polyethylene glycol group W. H. CANNON, Examiner. having from about 40 to about 500 ethylene oxide units. 10 

5. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF AN OIL OF LUBRICATING VISCOSITY AND A MINOR PROPORTION SUFFICIENT TO ENHANCE THE DETERGENT CHARACTERISTICS OF THE COMPOSITION OF A COPOLOMER HAVING THE STRUCTURAL FORMULA: 